Segmented stator with improved handling and winding characteristics

ABSTRACT

A stator assembly has discrete stacks of laminations. A plurality of nonmagnetic containment structures define pockets. The stacks are at least partially received in the pockets and coupled to one another by the containment structure. The containment structures are moveable between a first configuration in which the stacks are separate from one another and a second configuration in which yokes of adjacent stacks are in physical contact with one another. In a method of making a stator assembly, a plurality of stator segments are positioned so each is received in one of a plurality of pockets in a containment structure. Coils are wound around each stator segment while the containment structure prevents the stator segment from having direct physical contact with another stator segment. The containment structure is reconfigured to bring the wound stator segments into contact with one another, thereby forming a closed magnetic circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 11/534,705, filed Sep. 25, 2006, which is a division of U.S.Pat. No. 7,111,380, filed Apr. 30, 2003, which claims priority fromProvisional Patent Application Ser. No. 60/422,676 filed Oct. 31, 2002,each of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to stator assemblies for electromagneticmachines and, more particularly, to segmented stator assemblies in whichthe stator is formed from a number of discrete stator stacks or segmentswith each stator segment comprising a yoke portion, a tooth portion anda coil winding wound about the tooth.

BACKGROUND OF THE INVENTION

While the use of distinct and separately wound stator segments providessome benefits, it potentially increases the complexity and costs ofmanufacturing operations. For example, in many segmented stators thestator segments are wound individually and one or more manufacturingsteps are required to appropriately interconnect all the individualstator coils to form the phase windings. In such conventional statorassemblies, because the distinct and separately wound stator segmentsare not coupled together during the winding operation, some retentionstructure is required to hold the stator segments together when they areformed into an annular stator. The requirements for the coilinterconnecting step, the materials and equipment required for the same,and the need for a secondary retention mechanism often require asignificant capital investment in manufacturing equipment to manufacturesuch machines and significant material cost adds to the component costsof machines made according to such processes.

In an effort to overcome some of the limitations associated with statorassemblies having separately-wound stator segments as described above,approaches were developed wherein magnetically-interconnected statorsegments were physically coupled to one another prior to the windingoperation such that the coils could be formed in an interconnectedmanner. In known conventional approaches, the stator segments wereinterconnected though the use of hinges, sometimes referred to as puzzlelock connections, or through the use of thin interconnecting bridges ofmagnetically permeable materials. Such interconnecting structure oftenrequires relatively complex stator lamination constructions, which canincrease the overall manufacturing costs for a machine utilizing such adesign. Moreover, the manufacturing steps required to couple thedistinct stator segments together via the hinge or puzzle lock structureincreases the cost and complexity of the manufacturing process.

One limitation of stator assemblies using interconnecting puzzle piecesor bridges is that the stator assembly is often fairly inflexible andaccess to the stator teeth during the winding operation is somewhatlimited. These limitations can restrict the extent to which magneticwires can be placed in the stator to form the stator windings or, inother words, the “slot fill.”

An alternate conventional approach for forming a “segmented stator like”machine that does not require the use of hinges or puzzle locks reliesupon the use of a stator assembly formed from groupings of statorsegments that are magnetically coupled together by a thin,interconnecting bridge. Such a design is disclosed, for example, inJapanese Patent B-30107085. Through the use of such a bridge, it appearspossible to have a grouping of three stator teeth that are coupledtogether magnetically by a bridge element but that are opened to somedegree allowing greater access to the stator teeth and, thus, greaterslot fill. One limitation of this approach is that the stator assemblywill typically require more than three stator teeth such thatconstruction of the complete stator assembly will require the use ofmultiple groupings of three stator segments, which necessitates multiplemanufacturing steps of coupling the winding coils from the statorgroupings together and structure for coupling the multiple statorgroupings to form an annular stator. Such additional manufacturing stepsand structure can significantly increase the costs and manufacturingcomplexity associated with such stators.

The present disclosure describes several embodiments of a statorassembly that are designed to address the described and other limitingcharacteristics of conventional segmented stator assemblies.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a stator assembly.The assembly has a plurality of discrete stacks of laminations. Each ofthe stacks has a yoke and a tooth extending away from the yoke. Aplurality of nonmagnetic containment structures define pockets. Thestacks are at least partially received in the pockets. The containmentstructures couple the stacks to one another. The containment structuresare moveable between a first configuration in which the stacks areseparate from one another and a second configuration in which the yokesof adjacent stacks are in physical contact with one another to form amagnetic circuit.

Another aspect of the invention is a method of making a stator assembly.The method includes positioning a plurality of stator segments so eachstator segment is received in one of a plurality of pockets in acontainment structure. Coils are wound around each of the statorsegments while the containment structure prevents the respective statorsegment from having direct physical contact with another stator segment.The containment structure is reconfigured to bring the wound statorsegments into contact with one another, thereby forming a closedmagnetic circuit.

Still another aspect of the present invention is a method of making astator assembly comprising a plurality of stator segments and windingscoiled around the stator segments. A plurality of stator segments aresandwiched between first and second containment structures having aseries of pockets connected by flexible hinges so each stator segment isreceived in a pocket of the first containment structure and received ina pocket of the second containment structure. Coils are wound around thestator segments. The containment structures are reconfigured to bringthe wound stator segments into contact with one another, thereby forminga closed magnetic circuit.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate portions of an exemplary stator assemblyconstructed in accordance with certain teachings of this disclosureprior to the rounding of such a stator assembly into an annular form.

FIG. 2 generally illustrates an exemplary stator assembly constructed inaccordance with certain teachings of this disclosure after it has beenrounded into an annular form.

FIGS. 3A and 3B generally illustrate certain aspects of a hinge assemblythat may be used in connection with the exemplary embodiment of FIGS.1A-1C and 2.

FIG. 4 generally illustrates aspects of a stator assembly formed inaccordance with certain teachings of this disclosure and a process forwinding such a stator assembly.

FIGS. 5A-5C generally illustrate an alternate embodiment of a statorassembly that may be used in connection with the exemplary windingprocess described in connection with FIG. 4.

FIG. 6 generally illustrates an alternate embodiment of a hingestructure that may be used in connection with a stator assembly asdescribed herein.

FIGS. 7A and 7B generally illustrate alternate engagement/lockingstructures that may be used with a stator constructed in accordance withcertain teachings herein to retain the stator assembly in an annularform.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning to the drawings, and in particular to FIGS. 1A-1D, an exemplaryembodiment of an improved segmented stator assembly 10 constructed inaccordance with certain teachings of this disclosure is illustrated.

Referring to FIGS. 1A-1C, the stator assembly 10 includes a plurality ofdiscrete, non-interconnected stator segments 20 sandwiched between twocontainment structures 30 and 40. In general, the stator segments 20 areformed form stacks of substantially identical laminations. The statorsegments 20 are not directly interconnected or magnetically coupled toone another. The stator segments are positioned within and held in placeby pockets in the containment structures 30 and 40 that are designed andshaped to receive the stator segments. The containment structures defineflexible hinges that couple the pockets that contain the stator segments20 to one another. The containment structure is not magneticallyconductive. During construction, the independent stator segments 20 aresandwiched between the containment structures 30 and 40. Then, while thestator segments are isolated from one another by the containmentstructures 30 and 40, wire is wound about the teeth of the statorsegments to form stator coils and phase windings. After winding, thestator assembly 10 is rounded into an annular form, bringing the statorsegments into physical contact with one another and forming a closedmagnetic circuit to form a completed stator. Details of this exemplaryembodiment are provided below.

Stator assembly 10 includes twelve stator segments 20, althoughalternate embodiments with a different number of stator segments 20 areenvisioned and possible. The construction of each stator segment 20 issimilar to the construction of the stator segments used in conventionalsegmented stator assemblies. Each stator segment 20 is formed form astack of substantially identical laminations, typically stamped fromsteel. As best reflected in FIGS. 1B and 1C, each stack of laminationsdefines a main yoke portion 21 and an extending tooth portion 22 thatterminates in a “T” shaped portion 23.

The yoke portion 21 of each stator stack defines an engagementprojection 24 on one side of the yoke 21, and an engagement notch 25 onthe opposing side of the yoke 21. The engagement projection 24 and theengagement notch 25 are sized such that when adjacent stator segments 20are brought together the engagement projection 24 will be received inthe engagement notch 25. This inhibits relative movement of the adjacentstator segments 20 in at least one direction. Notably, unlike prior artconfigurations where interlocking puzzle pieces serve to physicallyconnect adjacent stator pieces together, the engagement notches andprojections of the exemplary embodiment do not perform that function.Absent some other retaining structure, the engagement notches andprojections will not physically interconnect or hold together adjacentstator segment pieces.

In addition to defining engagement notches and projections as describedabove, the yoke portions 21 of each stator segment also define a rearchannel 26. Rear channel 26 is sized to receive in a press-fitrelationship a portion of the containment structures 30 and 40 to helpcouple the stator segments to the containment structures. This isdescribed in more detail below.

The “T” shaped portion 23 of each stator stack 20 defines an outersection 27 that upon complete assembly will be exposed and define arotor bore and an inner section 28. The inner section 28 is configuredto help position and retain a motor winding coil in a desired positionwith respect to the stator tooth as described in more detail below.

As described above, stator segments 20 are not physically coupledtogether by hinges, interlocking puzzle pieces or other features thatare themselves part of the stator segments. To the contrary, no direct,stator segment-to-stator segment coupling exists between the statorsegments 12. The two containment structures 30 and 40 “sandwich” thestator segments to form a relatively flexible stator assembly that isrelatively easy to construct and wind. The stator assembly is heldtogether in a form analogous to a “rack-of-ribs” where, in an openarrangement as illustrated in FIG. 1A, the solid stator segmentassemblies 20 do not make contact and are not coupled together but areattached by a flexible member. The flexible member is the hinges ofcontainment structures 30 and 40.

Referring to FIG. 1C, details of one the containment structures 30 and40 are illustrated. In general, each of the containment structures 30and 40 comprises a flexible plastic structure that defines variousrecesses 50 a and 50 b or “pockets” in which a stator segment 20 may bepositioned and held. The pockets are held together by an integralflexible hinges. Slits and positioning features (not illustrated inFIGS. 1A-1D) are provided to ensure proper positioning of the windingcoils. Upon final assembly, these positioning features will be placedabout the stator poles.

The stator assembly is constructed so as to accommodate three phasewindings with each phase winding comprising winding coils wound aboutthe teeth of four stator segments 20. To accommodate the end-terminalsof the three phase windings, the upper containment structure 30 includessix terminal retention features 31 a, 31 b, 31 c, and 32 a, 32 b, and 32c that can be used to position and maintain the end terminals of threephase windings A, B and C (not illustrated in the figures). Each of theterminal retention features comprises a slit formed in the containmentstructure and a projecting post around which a portion of the terminalend of the phase winding may be wrapped to position the terminal end ofthe winding in a fixed location.

In addition to including the terminal retention fixtures, the pocketsthat form the containment structure 30 also define slits 33. These slitsallow the wires that form the phase windings to pass from the portion ofthe containment structure 30 that faces the interior of the rotor boreto the portion of the containment structure 30 that faces the exteriorof the stator assembly. As described in more detail below, the slits 33are positioned to ensure that the wires that form the winding coils arepositioned in a defined relationship to the stator assembly and to anyexterior shell member into which the stator assembly 10 may bepositioned.

Additional details of the pockets that form containment members 30 and40 are depicted in FIGS. 1B and 1C, which illustrate correspondingportions of the upper containment structure 30 and the lower containmentstructure 40 for holding a single stator segment 20. Neither the hingesthat would connect the illustrated portions of the containmentstructures 30 and 40 to adjacent portions nor the adjacent portionsthemselves are depicted in FIGS. 1B and 1C.

Referring to FIGS. 1B and 1C it may be noted that the containmentstructure 30 defines a top portion 53 that, when placed over a statorsegment 20, will generally rest on top of the stator segment 20. Thecontainment structure 30 further defines downwardly extending portions34 that extend downwardly from the top portion 53. The downwardlyextending portions 34 are shaped to slide over the extending portion 22of the stator segment. There are two downwardly extending portions 34for each pocket of the upper containment structure that will slide overand cover the opposing sides of the extending portion 22 of the statorsegment. As depicted in FIG. 1B1, the ends of the downwardly extendingportions 34 define a notched area 35 having a height H and a thickness Twhere the portion 24 changes from a first thickness to a secondthickness.

As further depicted in FIGS. 1B and 1C the lower containment structure40 defines a bottom portion that will rest on the bottom of the statorsegment. The pockets of the lower containment structure 40 furtherdefine upwardly extending portions 37 that extend upwardly along theextending position of the stator segment 20. As depicted in FIG. 1B2 theupwardly extending portions 37 define notched areas 38 that are sized tobe received in the notch 35 defined by the downwardly extending portionsof the upper containment structure 40.

The notched structures of the upper and lower containment structuresengage one another in a manner generally reflected in FIG. 1D such thatthere is no direct path through any opening from the exterior of theinsulating surface to the metal forming the stator tooth. Specifically,as reflected in FIG. 1D, the only path from the exterior of theinsulator to the metal forming the stator tooth would be though thesmall opening 200, and up the interface between the notched surfaces 35and 38 and across the small opening. This engagement of notched surfacesensures that the winding coils are adequately insulated from the statorteeth.

The upper and lower containment structures 30 and 40 further defineextending flanges at the end of the structures that fit near theT-shaped ends of the stator assemblies. The containment structures 30and 40 further define upper and lower projections 39 a and 39 b that areconfigured to fit into the channels 26 formed in the stator segments ina press-fit relationship to help join the containment structures 30 and40 onto the stator segments 20 and to prevent relative movement betweenthe stator segments 20 and the upper and lower containment structures 30and 40.

As FIGS. 1A-1C illustrate, when the containment structures 30 and 40 areplaced over a group of stator segments 20 such that multiple statorsegments are sandwiched between the containment structures 30 and 40,portions of the containment structures 30 and 40 will surround andencase the extending portions 22 of the stator segments 20.Additionally, containment structures 30 and 40 will provide aninsulating barrier between the region interior of the T-shaped portionof the stator segments 20 and the T-shaped end of the stator segmentsand between the region interior of the T-shaped end of the statorsegments and the portion of the yokes of the stator segments that willface inwardly towards the stator bore. When positioned about the stator,the containment structures 30 and 40 thus insulate any winding coilwound about the stator teeth of the stator segments 20 from the metalforming the stator segments. As reflected best in FIG. 1A, a portion 27of each stator tooth is not covered by any portion of the containmentstructures and such exposed section will extend into the interior rotorbore when the stator assembly is rounded into an annular form.

Additional details of the upper and lower containment structures 30 and40 are illustrated in FIG. 3A and FIG. 3B, which illustrate a top downview of a portion of an exemplary upper containment structure 30. Asillustrated, the containment structure 30 defines, for each pocket, anend portion 300 that fits over the T-shaped end of the stator assembly20. While not illustrated in FIGS. 3A and 3B, a similarly shaped portionexists on the lower containment structure 40. The end portion 300 isramped to define a surface that will tend to cause any winding coilwound about the stator teeth to be pressed into or retained within theslot that will exit between adjacent stator teeth.

FIGS. 3A and 3B further illustrate details of exemplary embodiments ofhinge 42 that connects the upper containment member 30. Similar hingesare found on the lower containment member 40. As illustrated, the hinge42 comprises a small region of thin plastic that couples adjacentpockets of the containment structures together. The hinge element 42 isa “living hinge” in that it is relatively freely bendable in bothdirections. Moreover, the point of the hinge at which the bending occursis substantially at the outer periphery of the stator assembly when thestator assembly is rounded into an annular form. FIG. 3A illustrates ahinge 42 in a closed configuration and FIG. 3B illustrates an exemplaryhinge 42 in a generally open configuration. The pockets of FIG. 3B arenot pockets associated with the terminals of the phase windings and, assuch, no terminal retention features are illustrated in the figure. Theslits 33 for allowing passage of the wire forming the winding coils fromthe interior of the stator assembly to the exterior of the statorassembly are illustrated in FIGS. 3A and 3B.

After the stator core segments 10 are positioned within the containmentstructures 30 and 40 to form a flexible strip assembly as depicted inFIG. 1A, winding coils are wound about the stator teeth so as to form aplurality of phase windings. In the example of FIGS. 1A-1D, windingcoils may be positioned to provide three phase windings, with each phasewinding including four winding coils. Other constructions are possiblewith the phase winding including fewer or greater numbers of windingcoils.

The phase windings are formed by the following process. First, beginningof one phase winding is inserted into a terminal retention feature.Then, a winding coil is formed about the appropriate stator tooth. Thewire is run out towards the back of the containment structure 30 througha slit 33, through the back of the portion of the containment structureassociated with the next two adjacent stator teeth, bringing the wire intowards the tooth of the third adjacent stator teeth through a slit 33in the relevant portion of the containment structure. This process isrepeated until all the winding coils for the phase winding are formed.

The winding procedure described above can be accomplished in a varietyof ways. In accordance with one exemplary winding process, a needlewinding process is used wherein the coils that form the phase windingmay be wound individually. In an alternate process, the coils that formthe phase windings are wound simultaneously with one needle beingprovided for each phase windings.

One of the benefits of the “living” hinge illustrated above is that thestator assembly 10, prior to being rounded into an annular form, can befully opened to allow greater access to the slot area for winding, thusallowing a greater slot fill and allowing for enhanced precision windingtechniques. The ability of the described embodiment to be fully open asdescribed above allows the stator assembly to be fly wound at speedsfaster than those that exist for conventional stator winding techniquesand potentially enables slot fills greater than previously available.

FIGS. 3A and 3B also illustrate yet another preferred embodiment of thepresent disclosure, where web 43 and shields 44 are added to create aclearance between the coils and the stator stack when rounded intoannular form. Web 43 and shields 44 run the entire length of eachsegment and are preferably made of plastic. As shown in FIGS. 3A and 3B,web 43 is designed in a manner so as to provide the flexibility toperform the winding process described hereinabove. Two shields 44 areprovided on opposite sides of each containment structure to ensure thatthe winding coils are adequately insulated from each stator tooth.

FIG. 4 generally illustrates a stator assembly 10 formed as describedabove in connection with FIGS. 1A-1D. In the illustrated statorassembly, there are to be three phase windings, A, B and C. In FIG. 4,each tooth of the stator is identified with a label identifying thephase winding to which it corresponds and the polarity of the winding tobe placed about the stator tooth. As those of ordinary skill in the artwill appreciate, by winding the winding coil about the stator tooth in afirst direction one is able to achieve an electromagnet of a firstpolarity when the winding is energized in a first direction. By windingthe coil in the opposite direction, when the winding coil is energizedin the same direction, it is possible to establish an electromagnet ofopposing polarity. Thus, FIG. 4 identifies each stator tooth as beingassociated with a phase winding A, B or C and a particular polarity + or−. The winding pattern of FIG. 4 is exemplary only and other windingpatterns can be used without departing from the teachings of thisdisclosure.

Referring to FIG. 4 it may be noted that the winding operation isperformed through the use of a tooling element 400 that engages featureson the stator assembly 10 so as to move the stator assembly 10 duringthe winding operation. The tooling element 400 moves the stator assemblyduring operation such that, at various times, the stator assembly ispositioned to expose differing stator teeth to enable easy and fastprecision fly winding. For example, in FIG. 4, the stator assembly ispositioned such that a set of stator teeth A−, B− and C− are exposed.Needle or fly winding techniques may be used to wind one or more of theexposed stator teeth. In this manner the stator assembly may be rapidlyand quickly wound.

Regardless of whether fly or needle winding techniques are employed, andregardless of whether the stator assembly is wound in a configuration asillustrated in FIG. 1A or in the open configuration of FIG. 4, theexemplary stator assembly disclosed herein is constructed such that thephase windings can be placed in the stator assembly with no more thanthree starts and three finishes. For example in a winding operationwhere each stator tooth is individually wound, a winding operation couldbegin with the stator assembly positioned such that a winding coil ispositioned about a first stator tooth (labeled A+ 402 in FIG. 4). Thewinding apparatus could then proceed to wind the next toothcorresponding to the phase A winding (labeled A− 402 in FIG. 4) withouthaving to stop the winding process or cut the wire forming the phasewinding. The process could continue until all of the teeth correspondingthe phase winding were wound. After the phase A winding was completed,the next phase winding could be wound on the machine.

The winding approach and processes described above allowing for an“open” winding of the stator assembly 10 as depicted in FIG. 4 can bebeneficially applied to stator assemblies having alternateconstructions, such as stator assemblies where the stator segments areinterconnected to one another directly by, for example, interlockingpuzzle pieces.

FIGS. 5A-5C generally illustrate a stator assembly 500 that is formedfrom stator segments 501 where the stator segments 501 are directlycoupled together by interlocking puzzle pieces. The construction of thestator segments 501 and the insulators 501 used with such segments issuch that the stator assembly may be fully opened to allow completeaccess to the winding. FIGS. 5B1 and 5B2 generally illustrate a statorsegment 501 of the type used in the embodiment of FIG. 5A. The statorsegment defines a yoke 502 and an extending tooth portion 503. The yoke502 further defines a projecting element 504 and a receptive element505, where the projecting element 504 is sized to fit into the receptiveelement 505 of a neighboring stator segment to create a chain-likestator assembly. The projecting element 504 defines upper and lowerrecesses and the receptive element defines upper and lower extensions.The upper and lower recesses are sized so as to receive the upper andlower extensions of an adjacent stator segment. This arrangement ofinterfering recesses and projections allows for the stator assembly tobe opened for full and fast winding as described above.

FIGS. 5C1 and 5C2 generally illustrate the form of insulating elementsthat may be positioned about the stator segments of FIGS. 5B1 and 5B2 toproduce the stator assembly of FIG. 5A. In general, the insulatingelements comprise plastic elements that fit over the individual statorsegments to insulate the winding coil to be placed about the statortooth from the metal that forms the stator tooth. Each insulatingelement has an upper component 510 and a lower component 512, where eachof the upper and lower components defines a top (or bottom) section thatforms an insulating barrier between the top and bottom of the statortooth and the winding coil and a downward (or upward) extension 514, 516that serves to insulate the winding coil from the portion of the yokethat faces the interior bore of the stator. Other insulating materials(not illustrated) may be used to provide insulation between the sides ofthe stator tooth and the winding coil. Referring to FIGS. 5C1 and 5C1,it may be noted that the insulating elements may further define aprojecting finger 518, 519. The projecting fingers 518, 519 may helpkeep the interlocking puzzle pieces from moving in an axial directionwhen the stator segments are coupled together, and thus tend to maintainthe engagement of adjacent stator segments. Because the stator assembly500 of FIGS. 5A-5C can be fully opened, it would be wound in accordancewith the “open” winding processes described above in connection withFIG. 4.

It should be noted that the use of the containment structures 30 and 40or the special interlocking puzzle elements of FIGS. 5A-5C allows forthe construction of a stator assembly where a flexible chain or stripcan be formed that contains all of the stator teeth that will be used toform the stator. Moreover, because the hinge 42 of the embodimentdescribed in connection with FIGS. 1A-1D and the chain connection asdepicted in FIGS. 5A-5D can be repeatedly opened and closed, it ispossible to wind the described stator assemblies in a variety of waysand using a variety of processes where the number of starts and thenumber of finishes used in the winding operation is not greater than thenumber of phase windings. For example, in the winding operationdescribed above in connection with FIG. 4 there are three startoperations and three stop operations.

While the living hinge 42 of FIGS. 3A and 3B allows for a windingoperation where the tooth to be wound is fully exposed, under certaincircumstances it is desirable to have a stator assembly that, prior towinding, is not as flexible as that previously described. It may also bedesirable that the hinge element is stiff such that the stator assemblyis relatively inflexible during the winding operation. Such a statorassembly can be achieved in a number of ways. For example, the hingeelement may be constructed of relatively thick plastic material suchthat flexing of the hinge during winding is inhibited. Alternatively,the containment structures 30 and 40, and therefore the hinge elementmay be formed from a relatively stiff material such that flexing isprecluded. Alternatively, the rounding of the stator assembly intoannular form may involve breaking the containment structure at the hingeelement. Still other embodiments are envisioned where the hinge isessentially as described above in connection with FIGS. 3A and 3B, butwhere some additional stiffening support is provided to inhibit flexingof the stator assembly during the winding operation. Such an embodimentis generally illustrated in FIG. 6.

Referring to FIG. 6, two adjacent pockets from a containment structureare illustrated. The pockets have the same general structure asdescribed above in connection with FIGS. 3A-3B, except for the inclusionof two retaining features 600 and 601 that may take the form of upwardlyextending pins and two receptive elements 602 and 603 that may take theform of a small holes or openings in the pockets. In the illustratedembodiment a stiffening member 604, that may take the form of a bentwire, a shaped resilient plastic piece, or other flexible, yet stiffform, is provided that engages the retaining members and receptiveelements and provides some stiffening of the hinge element 42. When thestator assembly is in the open, non-annular configuration, thestiffening remember will tend to prevent movement or flexing of thestator assembly as the strength of the stiffening member will beselected so as to overcome the bending forces that would typically beapplied to the hinge element 42 during a winding operation. Thestiffening member, however, would be selected to have a strength that isnot sufficient to overcome the forces that would be applied to thestator assembly during the operation where the stator assembly isrounded into an annular form. During that operation, the stiffeningwould break, or preferably bend to avoid the creation of any potentiallycontaminating particles, to allow the stator assembly to be rounded inan annular form. In this embodiment, the stator assembly would berelatively stiff during its winding operation, such that the windingoperation would proceed generally as described above (e.g., a windingoperation where each phase winding is wound on the machine and where thenumber of stars and stops is equal to and/or no greater than the numberof phase windings).

Once the stator assembly 10 as described above is completely wound,whether through an open winding operation as described in connectionwith FIG. 4, a winding operation with a stiffened stator assembly, oranother winding method, the stator assembly will be rounded into anannular form for use as a stator element. When the stator assembly is sorounded, the edges of adjacent stator segments will come into physicalcontact with one another, thus producing a closed magnetic circuit.

There are several approaches that may be used to maintain the roundedstator assembly in its annular form. In one embodiment, the roundedassembly is simply inserted into a motor housing or shell in a press fitrelationship such that the housing or shell serves to maintain thestator assembly in its annular form. In an alternate embodiment, someform of band or other external retaining structure may be used to circleor otherwise engage the annularized stator assembly so as to hold thestator assembly in the desired configuration. Still further embodimentsare envisioned wherein one or more of the containment structures areprovided with engagement or locking elements so that opposing ends ofthe stator assembly can engage and, thus maintain the stator assembly inan annular form.

FIGS. 7A and 7B generally illustrate two alternate engagement/lockingstructures that may be provided on the containment structures to holdthe stator assembly in an annular form. In the embodiment of FIG. 7A oneof the pockets on one end of the stator assembly is provided with aprojection 700 having a generally sloped front surface and a relativelyflat back surface. The pocket on the opposing end defines a receptiveelement 702 having a latching finger. When the stator assembly isannularized and the projecting element is moved into engagement with thereceptive element, the latching finger will lock down on the flat backof the extension 700 and tend to hold the stator in an annularized form.FIG. 7B illustrates an alternate configuration where a ball-and-socketform of engagement is provided.

It should be noted that the interlocking/engagement elements asexemplified in FIGS. 7A and 7B need not have a strength sufficient tohold the stator assembly in an annular form for all purposes. Suchengagement elements may be used to hold the assembly together forinterim manufacturing or testing operations while a motor housing, shellor other form of retention could be used a supplementary or alternateretaining structure effort in the final product.

One attribute that may be implemented in connection with the statorassemblies described herein is to route the wires used to form thewinding coils in such a manner that they do not pass over or even nearthe hinge portions 42 of the containment structures 30 and 40, whichbend when the stator assembly 10 is rounded to form an annular stator.In such an embodiment, features on the containment structure may beprovided to actively preclude and prevent the wires forming the windingcoils from passing over or in the vicinity of the hinges 42. Suchfeatures may help ensure that any motor constructed in accordance withcertain teachings of this disclosure meets any applicable requirementsthat electrical conductors be at least an inch inward of the outerdiameter of the stator assembly. These features further tend to ensurethat the wires forming the phase winding do not interfere with pressingtools necessary to press the stator assembly into a secondary retentivedevice (e.g., a stator shell) used to hold the stator assembly together.

In the embodiment described above, the features on the containmentstructures will generally ensure that the wires that form the phasewinding pass inwardly (i.e. on the rotor bore side) of the portion ofthe hinge element 42 where the bend occurs. Because the path of thewinding wire is inward of the hinge 42, there will necessarily be minorflexure of the windings when the bending operation is performed. Thefeatures of the containment structures may be formed such that anyflexure of the wire will be directed upward, downward or inward, but notoutward towards hinge 42.

While the apparatus and methods of this invention have been described interms of preferred embodiments, it will be apparent to those skilled inthe art that variations may be applied to the apparatus and processdescribed herein without departing from the concept and scope of theinvention. For example, in the embodiment illustrated in FIGS. 1B and1C, portions 34 and 37 of the containment structure serve to insulatethe side edges of the stator teeth from the coils that are wound aboutsuch teeth. While such an embodiment is appropriate for manyapplications, in applications where the stack height of the motor is notconsistent, such an embodiment may not be ideal as different containmentstructures would be required to provide the appropriate insulation fordifferent stack heights. Thus one alternate embodiment would be toeliminate such portions of the containment structures and use differentinsulating materials (e.g., insulating strips) such that the samecontainment structures could be used for motors of different stackheights. Still further, alternate embodiments are envisioned wherein thecontainment structures are formed form a highly thermally conductivematerial or are filled with thermally conductive resin or otherthermally conductive materials so as to aid in the removal of heat fromthe stator assembly during operation of the motor. Such modifications,as well as other substitutes and modifications are deemed to be withinthe scope and concept of the invention.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims.

What is claimed is:
 1. A stator assembly comprising: a plurality ofdiscrete stacks of laminations, each of the stacks having a yoke and atooth extending away from the yoke; and a plurality of nonmagneticcontainment structures defining pockets, the stacks being at leastpartially received in the pockets, the containment structures couplingthe stacks to one another, the containment structures being moveablebetween a first configuration in which the stacks are separate from oneanother and a second configuration in which the yokes of adjacent stacksare in physical contact with one another to form a magnetic circuit. 2.A stator assembly as set forth in claim 1 wherein the secondconfiguration comprises an annular configuration.
 3. A stator assemblyas set forth in claim 1 wherein each containment structure comprises ahinge for facilitating pivoting movement of the containment structurebetween the first and second configurations.
 4. A stator assembly as setforth in claim 1 wherein the containment structures are further movablebetween a straight configuration in which the teeth of each stack areevenly spaced and arranged in a line and an open configuration in whichthe yokes of at least some adjacent stacks are arranged in an accurateconfiguration such that the spacing between the respective teeth isincreased relative to the spacing of the straight configuration.
 5. Astator assembly as set forth in claim 1 further comprising a continuousfirst wire, a continuous second wire, and a continuous third wire, eachof the first, second, and third wires being coiled around at least oneof said stacks.
 6. A stator assembly as set forth in claim 5 whereineach of the first, second, and third wires is coiled around multiplestacks.
 7. A stator assembly as set forth in claim 1 wherein each of thestacks includes two opposite ends and a middle extending between saidends and the containment structures include a first containmentstructure positioned to cap one of said ends of two or more of thestacks and a second containment structure positioned to cap another ofsaid ends of said two or more stacks.
 8. A stator assembly as set forthin claim 7 wherein the first and second containment structures contactone another adjacent the middles of the stacks.